This invention relates to a recording apparatus for recording an information signal on a magnetic record carrier, the apparatus comprising:
an input terminal for receiving the information signal, PA1 a write driver circuit and PA1 a magnetic write head, the write driver circuit comprising PA1 a first voltage driver having an input coupled to the input terminal of the apparatus, and an output coupled to a first terminal of the magnetic write head, PA1 a second voltage driver having an input coupled to the input terminal of the apparatus and an output coupled to the second terminal of the write head, as well as to a write driver circuit for use in the recording apparatus. PA1 that the second voltage driver circuit comprises an output circuit of a series arrangement of an npn transistor and an impedance, coupled between said point of a first constant potential and the output of the second voltage driver circuit, the apparatus further comprising PA1 a first current driver having an input coupled to the input terminal and an output coupled to said first terminal of the write head, and PA1 a second current driver having an input coupled to the input terminal and an output coupled to said second terminal of the write head. The invention is based on the recognition to combine voltage drive and current drive techniques in order to obtain an improved recording apparatus.
Write drivers of the voltage drive type are well known in the art. Reference is made in this respect to U.S. Pat. No. 4,853,800 (D1 in the list of related documents that can be found at the end of this description) and DE-A 2,735,498 (D2).
There is a strong pressure, especially on hard-disk drive manufacturers, to increase bit density and to shorten access times. The current rate of increase in bit density (60 % per annum) is being sustained by a variety of technical improvements with a resulting increase in data rates of 40 % per year. In order to sustain this increase in data rates, the high frequency performance of the media, heads and electronics, in particular the write driver, have to increase at the same rate.
Conventional write driver techniques, based on current driving, see D3, current steering, see D4, have severe speed limitations. These limitations result not only from poor high-frequency performance inside the driver, but also from limitations imposed by the head-amplifier combination. In addition to the poor high-frequency performance of thin-film write heads, these shortcomings have become a major limitation in the write process for magnetic recording.